1. Technical Field
The present invention relates to a brushless motor. More particularly, the present invention relates to a brushless motor used as a driving source for an electric product such as a video tape recorder or a floppy disk drive.
2. Background Art
A brushless motor of magnet-rotating type comprises a rotor section having a rotor magnet, a stator section having a stator core around which windings are wound, and a driving circuit for controlling the current applied to the windings of the stator core or the like.
As shown in FIG. 13, the stator section of such a brushless motor comprises, for example, a core winding unit 43 composed of a stator core 41 and windings 42 wound around respective salient poles 41c, of the stator core 41; an electrical insulating resin type core holder 44 mounted on a circuit board 45 for supporting the stator core 41 and extending wires between windings 42 while being in the electrically insulated state to the circuit board 45; and terminals 51 fixed on the core holder 44 for relaying the electrical connection between the windings 42 of each phase and a driving circuit on the circuit board 45. Further, the rotor section comprises a ring-shaped rotor magnet 49; a rotor case 48 having the rotor magnet 49 fixed thereto; and a rotary shaft 50 for fixing and supporting the rotor case 48. The rotor section and the stator section are opposed to each other in such a manner that the rotor magnet 49 is positioned outside the stator core 41 and a gap is formed radially between the outer peripheral surface of the salient poles 41cand the rotor magnet 49. The rotary shaft 50 of the rotor section is supported by a bearing holder 46 fixed to the stator core 41. The bearing holder 46 is inserted from the upper part of the stator core 41 so as to pierce into a through hole 41a formed at the center of the stator core 41, a through hole 44a provided at the center of the core holder 44 and a through hole 45a on the circuit board 45, and is fixed to the circuit base board 45 together with the stator core 41 by means of a screw 47 so that a flange part 46a formed on the base of the bearing holder 46 is engaged with a shoulder part 41b of the stator core 41.
In the conventional brushless motor having such an arrangement, the windings 42 of the stator core 41 are electrically connected with the driving circuit (not shown) formed on the circuit board 45 through terminals, or by direct soldering when no terminal is used. For example, in the case of the brushless motor 40 shown in FIG. 13, the windings 42 of U, V and W phases are linked to the driving circuit on the circuit board 45 through terminals 51 fixed to the core holder 44 by a three-phase star connection. As shown in FIGS. 13 and 15, each terminal 51 is formed by a straight flat plate having a clipping portion 51a at a tip thereof and protrudes toward the circuit board 45, and then, the respective terminals 51 are fixed to the core holder 44 so as to be perpendicular to the circuit board 45. The front or rear end portions of the windings 42 of each phase are held by the clipping portions 51a protruding from the core holder 44 toward the circuit board 45, and tip portions 51b are soldered to land parts of the circuit board 45. By the way, the ends of the windings 42 are temporarily fixed to the terminals 51 by holding the ends of the windings 42 by the clipping portions 51a, and thereafter the ends of the windings 42 are electrically connected securely to the terminals 51 by fusing.
When the terminal 51 such as shown in FIG. 15 is used, however, it is necessary to have a space equal to a height H between the core holder 60 and the circuit board 45, since the terminal 51 protrudes so as to come into contact with the circuit board 45 vertically. The height H is obtained by adding the height (the length of a tongue part 51c branching from the body of the terminal 51) of the clipping portions 51a for holding the end of the winding 42, the space in which an electrode (not shown) for fusing can be arranged therein, and a length of a connection end portion 51b with which soldering is enabled. When using such a terminal 51, the reduction in the thickness of the brushless motor 40 becomes difficult. When the length of the tongue part 51c is shortened in order to reduce the height of the clipping portion 51a, it becomes difficult to hold the end of the winding 42 or the extending wire, since if it is not held, a failure may be caused. Thus, a sufficient length is required for the holder 51a.
Further, as shown in FIGS. 16 and 17, windings may be connected to a driving circuit by means of a core holder using no electrical connection terminals such as aforementioned terminals 51. This core holder 60 is formed by an electrical insulating resin type ring held against one plane of a ring part 64a of a stator core 64 which is on a side disposed on the circuit board, and its guide members 61, for supporting extending wires of the windings 68 wound around respective salient poles 64b of the stator core 64, are formed at six positions with an equal interval therebetween. Each of the guide members 61 comprises a wire guide part 62 projecting toward a circuit board and an overhang part 63 protruding like eaves in the radial direction of the motor above the wire guide part 62 in order to prevent extending wires from coming off. The core holder 60 is fixed to the stator core 64 by thrusting a plurality of protruding parts 67 into each hole 66 of a ring part 64a of the stator core 64, the plurality of protruding parts 67 being formed on the other plane of the core holder 60 opposite with the plane of the same having the projecting guide member 61. In the case of this core holder 60, the windings 68 are wound around each salient pole 64b of the stator core 64 while hooking and drawing the windings 68 at the guide parts 61 provided at six places as shown in FIG. 17, and the extending wires are adhered between the guide parts 61 to land parts of a driving circuit which are on a side disposed on the circuit board (not shown). The extending wires are fixed to the circuit board in the following manner. First, the extending wires between the guide parts 61 are pressed toward the circuit board and are brought into contact with corresponding land parts (portion designated by the hatching in the drawing) 69u, 69v, 69w and 69c. Thereafter, soldering is carried out. Second, the extending wire between specific guide parts 61, for example, the extending wire between V and W phases, is cut and eliminated.
However, when using the core holder 60 shown in FIG. 16, the coating of the extending wire between the guide members 61 must be peeled off while maintaining the winding as it is in order to carry out the soldering on the circuit board side, therefore, there is a problem of low productivity. In addition, when the windings 69 are soldered to the land parts 69u, 69v, 69w and 69c on the circuit base board, it is necessary to press down and sag the extending wires stretched between one guide part 61 and the other guide part 61, thus requiring the manual operation. Consequently, productivity is remarkably lowered. Further, since the midways of the extending wires are pulled toward the circuit board to be soldered on the land parts 69u, 69v, 69w and 69c, the extending wires may be snapped or the soldering may be come off due to the vibration or shock given to component members during or after the manufacturing of the motor, thereby deteriorating the reliability.